Efforts to enhance the appearance of automotive wheels have resulted in the development of the so-called "full face" fabricated sheet metal (e.g., steel) styled wheel, initiated in the 1980's by Motor Wheel Corporation, assignee of applicant herein, wherein the disc is a fabricated sheet metal part that extends generally radially outwardly around its outer periphery to also form the outboard tire bead retaining flange to achieve the full face appearance. A modified rim having dual bead seats but only a single, inboard tire-bead-retaining flange is separately fabricated from sheet metal, and the outboard rim free edge is formed to provide a radially in-turned flange which is welded to the inboard face of the full face disc part to permanently join the disc and rim parts in assembly. A commercially successful example of such a full face wheel is that disclosed and claimed in United States Overbeck et al U.S. Pat. No. 4,610,482, also assigned to the assignee herein.
As is well understood in the art, economical high volume manufacture of the disc part of disc-type fabricated sheet metal wheels, whether of the base or full face type, utilizes progressive die forming transfer press tooling and associated fixtures. Many forming stages as well as subsequent manufacturing operations are often employed to transform the flat circular sheet metal starting blank into the various configurations, contours and openings involved in providing the central bolt circle wheel mounting portion of the disc, the "window" or "beauty-section" of the disc which extends radially outwardly of the wheel from the center mounting portion, and, in the case of the aforementioned '482 patent type full face disc wheels, the reversely curved outer edge portion which forms the outboard tire bead retaining flange portion of the disc.
The other of the two main component parts of the aforementioned '482 patent-type full face wheel, namely the inboard rim part, has been separately made from the disc in a distinct and substantially different manufacturing process from that utilized in making the disc. Although each of these parts is constructed from uniform thickness sheet metal starting materials (such as plain carbon or high strength alloy steels, or less commonly, from aluminum and magnesium alloy sheet metal materials) the thickness of the full face disc starting material typically is almost twice that used for making the rim (e.g., about 0.200 inches versus about 0.100 inches in the case of steel alloys).
The rim part for the full face wheel is made by employing known rim making processes and apparatus. Some examples of such prior art rim rolling and edge conditioning processes and apparatus are disclosed in U.S. Pat. 3,077,130; 3,091,202; 3,364,550; 4,606,206; 4,825,675 and 4,848,125. The flat strip stock is first coiled and butt welded to form a cylindrical hoop, and then the inboard edge of the hoop is flared outwardly. The flared hoop is then subjected to a rolling operation to form, slightly undersize, the finished rim contour including the drop center well, inboard and outboard tire bead seats, associated safety humps and inboard tire bead retaining flange. The radially inwardly-curled outboard edge of the rim is formed in a final stage of the rim rolling operation by a specially formed roll and curling die or shoe. The rim is then subjected to a final sizing or truing operation in which the rim is expanded by segmental dies so as to be stretched to take a permanent set at a final size. Typically the starting thickness of the sheet material for the single flange rim part of the full face wheel is generally the same as that utilized in making base wheels having dual-flange rolled rims, generally on the order of 0.100 inches, and depending, of course, on the specified wheel material, size and load rating.
The disc part of the full face wheel is manufactured utilizing the aforementioned standardized disc making processes and apparatus which, like base wheel discs, generally involve die cutting the flat blanks from the sheet metal starting material and processing such blanks through multiple stage progressive die tooling in high speed transfer press equipment. For example, as many as eight or more stages may be required in the disc forming transfer press, e.g., (1) draw, (2) reduce, (3) form center and face, (4) trim O.D., (5) form edge, (6) pierce vent and medallion holes, (7) pierce bolt and center hole and (8) coin vent backside. See for example SAE Paper SP-897 entitled "Autobody Stamping Applications and Analysis" published February, 1992, pages 41-49, and in particular pages 47 and 48 thereof, as well as Swan U.S. Pat. No. 4,280,426, and Metals Handbook, 8th Edition, Vol, 4, pp. 182 (FIG. 48), published by the American Society for Metals (1969).
Due to the basic structural differences between a full face wheel construction of the aforementioned Overbeck et al type as compared to the conventional base wheel construction additional processing steps are employed in making the full face wheel disc part. In the rim part of a conventional base wheel assembly, the inboard and outboard rim flanges are both roll formed and shaped to final configuration in the aforementioned rolling operations from the same uniform thickness sheet material starting stock. Hence both flanges may be readily made to the same specified contour, thickness and other dimensional parameters to meet established Tire and Rim Association specifications for various standardized rim flange types such as "J, JP, JJ, and K" (which pertain to the rim flange contour on the tire side of the flange). Since the inboard and outboard flanges have essentially the same contour and thickness, the same type and size of wheel balance weight may be readily attached to either or both of these flanges.
By contrast, with a full face wheel construction the outboard flange is part of and integral with the disc part and therefore is substantially different from the roll-formed rim inboard flange. The final form which can be imparted to the outboard flange is thus limited by the characteristics of the wheel disc and the disc making operation as distinguished from the rim forming operations. Since the disc starting material generally must be substantially thicker than that of the rim stock, the disc outboard flange in its "as-stamped" condition likewise will be substantially thicker than the rim inboard flange. Also, it is not economically feasible in the progressive die forming operation to impart the required tire-side curvature to the outboard disc flange portion. Hence, in addition to being substantially thicker than the rim inboard flange, this disc outboard flange pre-form portion will generally have a radially outwardly flaring taper (relative to the wheel axis) as final formed in the disc making operation.
Accordingly, further rough and finish machining operations hitherto have been required on the disc to bring the disc outboard flange to the appropriate dimensions and configuration required to meet TRA specifications, as well as to satisfactorily accept and retain standardized wheel balance weights which can fit either or both of the inboard and outboard wheel flanges. The "as-stamped" disc full face part thus has been further processed in a pre-assembly machining operation in which the outer edge of the flange pre-form portion is first machined off to a predetermined "flange length" as a rough cut-out operation. This also removes most, if not all, undulations and other variations in the as-stamped pre-form flange circumferentially of the disc which may have been imparted in the progressive die forming operation.
In the next pre-assembly step, a further and final machining operation is performed in which the rough-cut disc outboard flange (in its die-made preform condition) is lathe form cut in a vertical axis lathe to impart the Tire and Rim Association specified tire side dimensions and configuration as well as suitable standard balance weight attachment contour. Typically, this has involved sequential lathe operations in which a form cutting tool first machines the radially outwardly facing inboard surface of the disc outboard flange to establish the required rim flange contour on the tire side. This operation has then been followed by a second form cutting tool operation to machine the radially inwardly facing outboard surface of the rim flange so that the final contour of the machined disc flange "curl" i.e., the outboard, radially inwardly facing contour in conjunction with the tire-side contour, is also suitable for accepting one of the standardized types of wheel balance weights.
The disc part, with the outboard flange so pre-machined, has then been fixtured to the rim part and welded thereto as set forth previously to initially form the two part full face wheel assembly. At this stage, or preferably in a following "pierce-after" operation, the geometric relationship of the finished dual rim bead seats and inboard rim flange are established radially relative to the wheel mounting openings, i.e., the mounting bolt holes and center pilot hole of the disc, as well as laterally relative to the central mounting plane of the disc. After this last metal working operation has been completed the full face wheel assembly is then ready for further processing in final conventional wheel coating operations such as painting, plating, etc.
As has been well understood by those skilled in the wheel making art, the aforementioned pre-assembly and after-assembly machining operations on the outboard disc flange represent additional manufacturing costs in terms of additional equipment and process operations which in turn increase the manufacturing costs of full face wheels relative to conventional base wheels. Accordingly there has been a well recognized need for many years to somehow reduce or eliminate such pre-assembly disc outboard flange machining operations to thereby reduce the as-manufactured cost of such full face wheels.
One prior art approach considered by the inventors herein to possibly solving some aspects of this problem is that represented by the prior manufacture, by the assignee of the inventors herein, namely Motor Wheel Corporation of Lansing, Michigan, of the so-called "Hollywood" type fabricated sheet metal full face styled wheels as produced commercially from the early 1960's until the late 1980's for rear wheel drive vehicles. Such a wheel is illustrated on page 26 of the April, 1965 issue of Motor Trend magazine and in FIG. 48 of the aforementioned Metals Handbook citation.
In the construction of this different type of full face wheel, as well as its manufacture as practiced commercially, the outboard bead seat and outboard flange were both made as die stamped preform areas in the disc, and then conjointly roll formed after welded assembly of the disc preform to a half rim inboard part. Suffice it to say at this point that, due to the differences in construction of this early type of fabricated full face wheel relative to the aforementioned Overbeck et al type, as well as the industry standards then prevailing as to balance weight attachment (inboard flange only), the processing techniques and equipment employed to produce such Hollywood wheels have not been found to be a satisfactory solution to eliminate the need for the aforementioned outboard flange machining operations.